1. Field of the Invention
This invention generally relates to a communication apparatus and method for use in transmitting an image that is inputted at a predetermined resolution, as an attachment to an electronic mail and a program for implementing the method.
2. Description of Related Art
In recent years, there has been developed an internet facsimile apparatus having a facsimile function and an electronic mail communication function that is executed through a public communication network.
The internet facsimile apparatus is capable of reading an image, converting the read image into an electronic mail data format, attaching it as a file to an electronic mail, and transmitting the electronic mail with the image attached to a desired destination through the Internet.
Such an electronic mail with an image attached is transmitted to a designated address via a mail server of an electronic mail exchange system on the Internet. The transmissible data capacity (data size) of an electronic mail is not standardized, but is usually restricted to a capacity that is specified by an administrator of a mail server. For example, the maximum transmissible data size of an electronic mail is set to several megabytes. Mail servers on the Internet have different capacities for handling electronic mails. No communication protocol has been established for exchanging the data of an electronic mail per communication between mail servers.
For example, if the above-stated conventional internet facsimile apparatus reads a plurality of document images at a high resolution and transmits the plurality of read images attached to an electronic mail, or if the conventional internet facsimile apparatus reads ten to twenty document images at a low resolution and transmits the reads images attached to an electronic mail, the data size of the transmitted electronic mail may be too large as to exceed the maximum capacity of a mail server per communication.
An electronic mail, whose data size exceeds the maximum capacity, cannot be transmitted to a destination address, and an error notification mail for this electronic mail is returned from a mail server. The error notification mail is a DSN (Delivery Status Notification) mail described in RFC (Request For Comments) 1894.
However, a user who gives an instruction for transmitting the electronic mail cannot know the data size of the electronic mail or the maximum capacity therefor although he or she can know the occurrence of an error in the transmission of the electronic mail due to the error notification mail. Thus, a user needs to read a document at a low resolution and attach the read document to an electronic mail, and divide an electronic mail into plural pieces to reduce the data size of an electronic mail to be transmitted. The data size of an electronic mail is not reduced based on a certain standard but is reduced arbitrarily by a user, and thus, the same error may occur in the transmission and retransmission of an electronic mail. This necessitates repeating the procedure for reducing the data size of an electronic mail. That is, if an error occurs in the transmission of an electronic mail due to the excessive data size thereof, it takes much time to retransmit the electronic mail.
Further, since the transmissible data size differs according to destination addresses, the data size must be adjusted according to destination addresses. This makes the electronic mail transmission very complicated.